1. Field of the Invention
This application relates to orthodontic appliances capable of applying a primary force to a jaw, the reaction from which force is applied to the exterior of the head and/or neck by an extraoral force-reaction device.
2. Prior Art
A device for applying primary force to a jaw by an intraoral device and exerting the reaction force on an extraoral force-reaction device engageable with the wearer's head or neck is shown, for example, in the Armstrong U.S. Pat. No. 3,526,035. The appliance of the present invention constitutes an improvement over the apparatus shown in that patent. A device for applying a force to an intraoral device utilizing a compression spring is shown in DeWoskin U.S. Pat. No. 3,772,789.
3. The Problem
The problem which has not been solved by prior orthodontic devices has been provision of protection against injury by snapback of the intraoral device should the intraoral device be pulled from the patient's mouth and released while it is still connected to the force-producing unit, or even if the tips of such device were merely disengaged from their tooth band sockets and the device then released while such tips are still in the mouth. Such snapback could occur by a patient improperly removing the device, or by childish pranks, or by a part of the headgear being caught by either a stationary or a moving object. This problem has been recognized as discussed in Snead U.S. Pat. 3,903,604 at column 1, lines 21 to 31, for example. Even if the tips of such device were not pulled from the tooth band sockets a yank on the headgear resulting from such catching would cause discomfort and possible injury.